Li Shimin took seventy men to ambush the prince at Xuanwu Gate. Why does Tang Gaozu know nothing about such a big sport?

Because when Li Shimin planned to change the Xuanwu Gate, everything was secret and Tang Gaozu could not know. Once he knows, he may get in the way, or send someone to inform Li not to come over, or send troops to suppress it, and it is impossible to give this opportunity.

And after so many years of secret development, Li Shimin's influence in North Korea can be said to be very great. Many people openly supported Li in front of the emperor, but secretly supported him. So the change of Xuanwu Gate went smoothly, and these people helped Li Shimin a lot.

We all know the TV series Chang 'an at twelve o'clock. Chang 'an has 12 gates, and each gate is heavily guarded. When you want to get in and out of this gate, you must have the emperor's instructions. It is conceivable that Li Shimin's power reached what level at that time. You can control this 12 gate in your own hands.

Moreover, when the Xuanwumen Rebellion happened, Tang Gaozu was still in a meeting with some ministers of the imperial court. These ministers were also arranged by Li Shimin to some extent, just to keep Tang Gaozu busy and let him do something, so that he wouldn't realize it and then have a chance to participate.

Finally, when Weichi Gong arrived at the temple covered in blood with weapons, he was shocked and didn't know what had happened. When Weichi Gong told him that several of your children were fighting outside Xuanwu Gate and two sons were executed by Li Shimin on the spot, he really understood what had happened. At this time, it was too late to do anything.